This invention relates to polyolefin adhesive compositions, a method of making thereof and articles made therefrom.
Hot melt adhesives (HMAs) have become part of everyday life. With the development of high speed manufacturing and processing equipment, hot melt adhesives can be found in many applications. These ranges from furniture and shoe manufacture, to packaging applications, to the production of baby diapers and cigarettes.
A HMA is a thermoplastic material, which is solid at room temperature, and which is applied in its molten form to a substrate and which will adhere to the surface of the substrate when cooled to a temperature below its melting point. They differ from other liquid adhesives in that they set simply by cooling rather than by chemical curing or the evaporation of a solvent.
As HMAs are 100% solid systems, they reduce transportation and storage problems. The instantaneous bond strength supplied by these adhesives has allowed the development of high speed production machinery. Their higher viscosity compared to solvent based systems allows them to be used on various porous and non-porous substrates without sacrificing bond strength. In addition, because they do not set by means of solvent evaporation, they do not create a pollution problem. This latter fact is becoming increasingly important with the rising environmental awareness.
In HMA compositions, wax having a low viscosity may be used to reduce the high viscosity of the high molecular weight polymer component and resin to ensure efficient mixing. This reduction in viscosity is particularly important during the application stage. A low viscosity helps pump the molten adhesive from the storage tank to the application area and to ensure proper surface wetting of the substrate when applied. US 2008/0081868 discloses such a HMA composition in which a wax is present.
The degree of crystallinity and the congealing point of the wax in the adhesive composition influences the open and set times of the HMA, as well as the flexibility and elongation properties. Wax also plays a major role in decreasing blocking of a pelletized HMA adhesive composition to prevent the adhesive pellets from sticking together during transport and storage. The high temperature properties of a hot melt adhesive are also largely controlled by the melting range of the wax which is used.
The packaging industry favors adhesive compositions with a fast set time, setting in less than five seconds from a molten state at conventional packaging operating temperatures to a solid or quasi solid having favorable Dot T-Peel, fiber tear and/or combinations of the aforesaid adhesion properties. Hot melt polymer based adhesives performing within this window are a favorable alternative to conventional formulated adhesives.
Accordingly, there exists a current and long felt need for adhesive compositions that overcome known deficiencies in conventional compositions and that have advantageous processing properties.